fix(p10-1a-2): PR review round 1 — doc inconsistencies + observable backfill error path

PR #140 회차 1 actionable 7건 반영:
- docs/SMOKE.md: parser_version "code-rust-ast-v1" → "code-rust-v1" (chunker_version 과 혼동); jq path .citation.code_lang → .citation.lang (wire 의 code_lang 은 SearchHit top-level)
- docs/ARCHITECTURE.md: Mermaid pcode→ptypes 잘못된 edge → pcode→core 로 정정 (kebab-parse-code Cargo.toml 실제 dep 와 일치); 디렉토리 트리에서 code-rust-ast-v1 chunker 표기 위치 kebab-parse-code → kebab-chunk 로 정정
- crates/kebab-app/src/app.rs: backfill_repo 의 .ok().flatten() 실패 silent swallow → tracing::warn 로 관측 가능, 비-abort 의도 보존
- crates/kebab-parse-code/src/rust.rs: impl_item arm 의 "function_item 만 unit 생성" 1A scope 한정 주석을 외부에서도 보이도록 arm 상단에 한 줄 추가 (내부 주석은 유지)

verify: kebab-parse-code 7/7 / kebab-app --lib 51/51 / code_ingest_smoke 3/3 green; touched-crate clippy clean (재부팅 전 검증).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/kebab-parse-code/src/rust.rs

@@ -249,6 +249,10 @@ fn build_blocks(
                         units.push((format!("{prefix}{name}!"), s, e, true));
                     }
                 }
+                // `impl` blocks: emit one unit per inner `function_item`.
+                // Associated consts / types / non-fn members do not become
+                // their own units in 1A (plan §1A scope; HOTFIXES will log
+                // if a future need arises). See inner comment below.
                 "impl_item" => {
                     glue.retain(|(_, gs, _)| *gs < s);
                     flush_glue(glue, units, &prefix);